The present invention relates to the field of post-tensioning concrete structures, and the methods and apparatus for forming the same. More particularly, the invention relates to a pocket former and methods of forming a pocket surface for assembling a post-tensioning concrete structure.
Post-tensioning is a process where high strength cables are embedded in concrete and tensioned after the concrete cures. The residual tension that is retained in the cable increases the tinsel strength of the finished concrete structure. Cable ends are secured within the concrete with specially designed steel anchors. Cable assemblies are pre-manufactured specifically for a given job. The cable assemblies include a complete assembled anchor on the “dead end” and a “free end” that is assembled on the job site.
The free end assembly is comprised of a standard anchor to transfer cable tension to the concrete, tapered retainer keys to secure the cable to the anchor, a pocket former to create a void in the concrete where tensioning jacks are attached to the cable, and finally grout to seal the finished assembly.
Removal of the pocket former after the concrete has cured is usually done by gripping the plastic ribs and pulling or prying the pocket former out of the pocket. This often causes serious damage to the pocket former making them non-reusable. Additionally, during concrete placement, concrete occasionally leaks between the second rim of the pocket former and the concrete form. This leaked concrete hardens and prevents the removal of the pocket former.
Therefore, a principal object of this invention is to provide a pocket former that reduces the incidence of concrete leakage between the second rim of the pocket former and the concrete form.
Another object of the invention is to provide an improved method and apparatus for applying removal forces to the pocket former that minimizes damage to the pocket former.
A further object of the invention is to provide a pocket former that produces a concrete void or pocket with improved surface geometry to promote adhesion of grout.
These and other objects will be apparent to those skilled in the art.